Device for selection of groups of lines within automatic telephone exchanges



May 2, 1950 E. A. ERlcssoN 2,506,200

DEVICE FOR SELECTION 01:7' GROUPS 0F LINES WITHIN AUTOMATIC TELEPHONE EXCHANGES.

3 Sheets-Sheet l Filed April 12, 1946 0 J@ n 6 m.

May 2, 1950 E. A. ERICSSON 2,506,200

' DEVICE FOR SELECTION oF GROUPS oF-LTNES WITHIN AuToMATTc TELEPHONE EXCHANGES Filed April 12, 1946 3 sheets-sheet 2 May 2, 1950 E. A. ERICSSON 2,506,200

DEVICE FOR SELECTION OF' GROUPS OF LINES WITHN AUTOMATIC TELEPHONE EXCHANGES 3 Sheets-Sheet 3 Filed April 12, 1946 .w 0 6 .R www* e c NS. L KW) l i M, u U f Y Ml. 4 V H uw I A AV .Mm g \|l. nu a Y NL um ITIIIIIILNlI :c |nv. R a j t@ L@ l 2 .11W Mh v :Uhl "H- `0 U) h ...t L la .5m m nu ...MV (Inf-JI' 4W.. i. IHN w. o .f'n Nn. Q H j TL i Illlll S S .2Q im im# u Patented May 2, 1950 v'DEVICE EUR LINES WITHIN-AUT EXCHANGES 'Eric Arvid SELECTION F yGROUPS 0F OMATI'C TELEPHONE Ericsson, Stockholm, Sweden, assignor to Teiefonairtiebolaget L M Ericsson, Stockholm, Sweden, a company of Sweden Application lin Sweden D 1 Claim.

The present invention relates to automatic telephone plants at which selectors are set wholly or `partly under control of a registering device. It `is an vobject or" the invention to arrange and from a registering device to control the setting of the selectors of a telephone plant so that the number of groups of lines and outgoing trafc directions 'from the different selector steps are increased beyond the number .of the groups of lines corresponding to the positions of the selectors in their. rst setting movement. Thus larger groups of subscribers lines may be'obtained besides which the number of selector steps is reduced which entails considerable savings of expense. According to the invention this is achieved thereby that at automatic telephone plants, within which speaking connections are arranged by aid of selecting devices having each two setting movements., of which the rst is used for selection of a group of lines among a number of groups ci lines, all or certain ol said lgroups of lines in their turns are divided into subgroups and a registering device combined with a link circuit, over which-a speaking connection is to be set, records at least a characteristic for the -rst series ci impulses for this connection coming in to said link circuit, whereupon said registering device by signals controls each .or certain selectors in the following speaking connection to selectone of the subgroups available in the second setting movement of the selector in dependenceupon said characteristic.

The linvention will be more closely .described with reference to the accompanying drawings, Figs. 1-3.

Fig. lishows a cor-d line withv appertaining group selectors CVI and a registering device consisting of the relays RSS- HL Fig. 2 shows asecond and a thirdgroup selector respectively with a-ppertaining control relays.

Fig. 3 shcwsa final selector with its control relays.

All selectorsvare step-by-step driven and have l0 positions in the iirst setting movement and 20 positions in the secondV setting movement. .For each position in the first setting movement is a muitiple frame with 20 lines. The 20 lines ina multiple frame for group seiectors :are divided in two groups of lines representing two. different trai-ric directions. frame for final selectors belong to one group of l0() subscribers" numbers and the l0 other llines in the same frame belong to another group of 100 subscribers numbers. The said two groups of "i60 subscribers* numbers belong iso-different thou- The 1U 'lrstlines in multiple l April 12, 1946, Seria'No. 661,576

ecember 13, 1943 (Cl. 17g- 18) Vindicated in the figure.

sands of subscribers numbers, as will be described below.

The system v'here described is an automatic telephone system for v80,000 subscribers. The first digit 1-8 in the called subscribers number sets the group selector GV'I in Fig. 1 and is recorded on the relays RSS-RSI!) whereupon the group selector GVI is restored to normal. The second digit sets the group selector GVI in its first 'setting movement. If the first digit is 1-4, the group seiect-or GVI selects a line among the iirst l0 lines, available by its seco-nd setting movement. lf the first digit is 5-8, the group selector selects a line among the later 10 lines available by its second setting movement. Thus 20 outgoing traflc directions are obtained from the group selector GVI.

The third digit sets a second group selector GVII Fig. 2 in its rst setting movement. Ii the first digit in the called subscribers number is 1, 2, 5 or 6, the group selector GVII selects a line among the first l0 lines in the multiple frame to which it is set. If the first digit is 3, 4, '7 or 8, the group selector GVII selects a line among the later l0 lines in `said multiple frame.

VThe lith digit sets a final selector, LV Fig. 3', in its Erst setting movement. If the rst digit in the -called number is 1, 3, 5 or 7, the nal selector is only set in its second setting movement by the last digit in the telephone number. If, however, the i'irst digit is 2, 4, 6 or 8, the final selector takes 10 steps in its second setting movement in the pause between the 4th and 5th digit, whereupon the 5th digit steps the final selector to a line among the last l0 lines in a multiple frame for final selectors.

The subscriber AB in Fig. 1 calls the telephone exchange and is in some known manner connected over a line finder, the wipers of which an, bo are The positive pole of the exchange battery, lin the sequel called positive, is in the figures indicated with -land its negative pole, in the sequel called negative, with The feeding relay RSI attracts its armature when the line finder has been set on the line corresponding to AB. The contacts il and i2 are actuated, relay R85 receives current and attracts its armature. Contacts l-i's are actuated. Thus a buzzer tone is connected to the subscribers line through the following circuit: positive, winding on relay contacts 38, and i3d, to the buzzer signal generator Su. The buzzer tone is induced over to the feeding windings on relay RSZ, passes two co-nd'ensers connected between the relays .Rsi and RSE and reaches the wipers ao be and the subscriber AB. The subscriber may now begin the impulse sending from his dial. t the first break of the circuit over the subscriber-s line the relay RSI releases its armature. The contact II opens but the relay RS remains actuated since it is slow-releasing. rIhe contact I2 is closed and the following circuit is formed: positive, contacts I2, 52 and I2 I, winding on magnet XMS, to negative. Parallel with the winding on the magnet XMS there is a winding on the relay RSE. The magnet XMS and relay RSS attract their armatures. The group selector GVI moves one step, the contacts I3I and 34 are broken and I32-l33 closed, the wiper X is moved to contact I. Simultaneously the contacts EBI- 56 are actuated. At the end of the first dial impulse the relay RSI again attracts its armature. The contact I 2 is broken, the magnet XMS releases its armature. The relay RS@ however, holds its armature a short while since the relay is slow-releasing through the following circuit: negative, both the windings on RSii in series, contacts 74 and B, to negative. At the next impulse from the dial, RSI again releases its armature, XMS and RSE are again magnetized,

wiper X is moved to contact 2, GV I is again moved 1 one step and so on. When the impulse series from the subscribers dial ceases, the relay RSE releases its armature and a circuit is completed from positive over the contacts 53, 35 and 3Q, the wiper X and the contact to which the selector GV! is set, a combination of the windings on relays RSS-I l), to negative. That or those of the relays RSS, RSQ or RSI() which are magnetized in said circuit, attract their armatures and are self held over their contacts 83, 92 and IUS respectively. Then the following circuit is completed: positive, contacts T2, 65 and 31, one of the contacts 8, 93 or iM, winding on the reset magnet ZMS, contact H32 to negative. If the group selector is set to position I, none of the relays RSS-lil attracts its armature, the following circuit being instead completed when relay RSS releases its armature: positive, contacts 53, 35 and 64, wiper X, contact l, winding on magnet ZMS, contact I32,'to negative. The magnet ZMS attracts its armature, contacts I4 I -I 43 are actuated and the selector mechanism is restored to the initial position. During the reset process the magnet ZMS is self-held with current over contact Ifil. Over the contact |42 the following circuit is completed: positive, contact 12, 65, I33 and M2, winding on relay RSS to negative. The relay RS3 attracts its armature and the contacts 3I-39 are actuated. Simultaneously the start circuit for the searching movement of the group selector is broken by the contact i113. When the group selector returns to its initial position the contact 32 opens and the magnet ZMS releases its armature. Relay RSS is self-held with current over the contacts 53, 36 and 43.

At the next impulse series from the dial of the subscriber the operation above is repeated but the circuits over the contact 35 and the contact 3'! are now broken and therefore no alteration in the position of the relays RSt-I takes place and the reset magnet ZMS is not actuated. Instead is, after the second impulse series, the contact 39 closed and the driving magnet YMS receives current in the following' circuit when relay RS releases its armature after the second impulse series: positive, contacts 72, 55, 33, 43, I5I and 39, winding on magnet YMS to negative. The magnet YMS attracts its armature and moves the wipers a, b, c, d, one step into the multiple to the first line in that group of lines before which the group selector is set by the second digit. The

self-breaking contact I5I is broken and the magnet YMS releases its armature, and so on. The wipers a, b, c, d are progressed over the multiple contacts in said group of lines. Two cases may non7 be distinguished.

(l) If the first digit in the subscribers number was 5, 6, 7 or 8 the relay RSI!) has attracted its armature and is self-held over the contact |03. The contacts lUI and H32 have been actuated. The test circuit of the group selector is now broken until the contact device K1 is actuated, the contact Ii l and the contact H2 being closed. The contact device K1 is actuated when the group selector has passed for instance half the number of the lines in the group of lines determined by the second digit of the subscribers number. Thus the following test circuit is completed: positive, contact 5i, winding on relay RS?, resistance r2, contacts m2 and H2, the c-wiper of the group selector to negative over the winding on relay RGi in Fig. 2 in some free group selector GVII. On finding a free group selector the relay RSI attracts its armature. The contacts 'II- 14 are actuated. The contact 'H disconects the resistance r2, the contact 'l2 breaks the circuit of the driving magnet YMS so that the searching movement ceases, the contact i3 closes a circuit for the relay RSE in series with the protection resistance r1 and the contact 'I4 prevents that a circuit is formed over the contact 66. The relay RSG attracts its armature and the contacts 6 i-S are actuated.

(2) If the first digit in the subscribers number was 1, 2, 3 or 4 the relay RSI!) has not attracted its armature and thus the test circuit of the cwiper of the group selector is closed over the contacts mi and iII during the rst part of the searching movement of the group selector. If no free line is found the contact device k1 is actuated and the contact Iii broken. The test circuit is thus broken during the later part of the searching movement.

The multiple of the group selector GVI is thus divided into two halves, the one in front corresponding to the digits 1-4 as first digit and the back one corresponding to the digits 5 8 as first digit. The digits 1 4 and 5-8, respectively, differ however by the relays RSS and RS9 being actuated in diferent combinations, which are signalled to the following group selector steps on the speaking lines a and b. Neither the relay RSB nor the relay RSS has attracted its armature if the first digit is l or 5 and no special signal is sent on the aor the b-line. The following group selector GVII according to Fig. 2 is set by the third digit in the subscribers number. The impulses from the subscribers dial is repeated by the relay RSI in Fig. l to the following circuit: positive, contacts I2, 52 and '53, the d-wiper of GVI, Contact I23 in Fig. 2, winding on magnet XMG to negative. Parallel with the magnet XMG the relay RGZ receives current through its one winding and attracts its armature. The contacts 2I-25 are actuated. The magnet XMG steps out the group selector GVII to the position corresponding to the third digit in the subscribers number. The relay RGZ is slow-releasing since the contact 24 keeps the windings of the relay short-circuited during the breaks between the impulses, the relay thus holding its armature during the whole impulse series corresponding to the third digit in the subscribers number. After the end of the impulse series the relay RGZ releases its armature. The relay RGi hasalready earlier attracted its armature, namely when the group selector GVI .stopped on thev `multiple. ,corresponding lgroup selector, connections m in Fig.

were separated from the digits- .the .group selector The-contacts; fifi: t4 were theny actuatediand ,thusufthe following .circuit is completed when relayy RGZ releases. its. arm alture: positive, contacts. 25', :l;3,'.34, .|33gandf 151|., -on the driving magnet to negative. The group selector GVII lstarts-in a free choice and searching `mier Athe flinessin the traffic direction indicated by the :third digit in the-subscribers number. 's ince no signal lhas reached-the speak ing lines .a andib. the relay R64 hasnot attracted rits armature and thus 'the following test circuit iis formed: positive, contact 'I winding 4on relay RG3, resistance r4, contacts 4| and the c-,wiper `.of the group selector AG'ZI'I'to Y'negative over thef winding on -relay 'RGl in some free selector Jin the :next selector step. The group selector GVI'I .will test only over those :lines 'in .the group of lines indicated by the third digit of the subscribers number, which lie foremost in the group of'lines.

vThus when a number of lines, for instance corre- Av.Spending to half the free choice-capacity, has been passed, the contact device k2 is actuated and `thetest circuit is broken in the contact H for the .remaining lpart of the searching movement.

As is shown in Fig. z-.sthe group selector GVI'I .may be connected in two .different ways: either is .the connection n or the connection m inserted. Which of the two connections that is to be in- @sertedris determined' bythe selector step to which the group selector belongs. Here is supposed that the group selector belongs to the second selector step, i. e. receives the third digit -in the subscribers number and 'that'the connection m is inserted. 'Ii relay'RSS in Fig. 1 has attracted its `armature and the contact 5| is closed. As soon as the selector -GVI is connectedwith the group selector GVII the following circuit is completed: positive, contacts 9|, 32, 44 and 6|, the a-wiper of the 2, contact |2|, winding on relay 'RG'4 to negative. vThe relay RG4 attracts its armature and the contacts 4 |43 are actuated. The relay RG4 is selfheld with current over the contact 43. When the group selector GVII is set by the impulse series corresponding 'to the third vdigit in the subscribers number the contacts |2||23 are actuated and the circuit which runs over the connection m is broken in the contact |2| and separated from the c-line. At the following search-- ing movement the test circuit of the relay RG' will not beclosed until the contact k2 is actuated and thus the following circuit is formed positive,

contact winding on vrelay RGS, resistance r4,

contacts 42 and H2, the c-wiper of the selector to negative through the winding onrelayy RGI in some free -selector in the next selector step. `The relay RG3 attracts its armature and the contacts 3|-34 are actuated. The contact 3| disconnects the series resista-nce r4. The lContact 34 lbreaks the circuit `for the driving magnet YMG. The contact 32 closes a circuit forfthe relay RG2 over the Vresistance r3 and `the Vcontact 33'preventsth'at a Ac'rcuit is arising over the con.- tact'24- The-relay 1R62 attracts 'its armatureand the contacts 2|-,25 are actuated. 'The speaking lines a and b are closed by the -contacts 2| and 22 and the impulse line ltact 23.

The groupy selectors in the third .selector-step are performed according to Fig. 2 but insteadof the connection mthe .connection n. is: mounted. In the first .groupselector piece the .digits 'ir the first digit is .13,4, 'l or -8 the).

d'is closed over the :ccn-

-5-:8 and in the all 0 l.second group. selector .step the digits 31,-,.2 were separated from the digits 3 4 and the digits .5 6 -ilom the digits 'l-. In the third group .selector step'the digits 1 and '2, 3 vand 4, 5 and P6, Tand 8, respectively shall be separated. This occurs by aid ofthe relay in Fig. 1. The -relay R58 attracts its-armature and one of the .digits 2, s, 6 crc-is dialled as the first kdigit in the subscribers number. 'lll'ius the contacts 8|-84 vare actuated. When; according to the description above, the relay RS3 attracted vits armature, the windings Aon Athe relay RS4 were connected over the con -tact 34 to the b-line. That winding, which is connected between the contacts 8| and 82 has :a high resistance and the winding which lies connected between the contact 32 and negative has a rather lowA resistance. When a second group vselect-0r connects itself to a third group selector the following circuit is completed: negative, one or bothwindings on relay RS4, one of the contac-ts 8| or 82 contacts '34, 4| and 62, the b-wiper of the first group selector, contact 22 in Fig. ,2, the 1J-wiper oi the second group selector, contact 2i! in the third gro-,up selector, connection A11., winding on relay RGliyto-positive. The relay RS4 in Fig. 1 attracts its armature independent of the circuit running over the contact 8| or the contact'82. The contacts 4 |-45 are actuated and relay RS4 is self-heldover the contact 42. The circuit of the -relay RSS is broken in contact 43 and' the relay R53 releases its armature, the a-'line 'being thus closed in contact 3| and the b-'line in contact 33. vAs long `as the circuit of the relay RS4 is closed the a.- and b-lines are still broken in the contactsl 44 and 4|, `respectively. If vthe relay RSS in Fig. 1 has attracted its armature, the. relay RG!! inFig. 2 attracts its armature. If', onthev contrary, the relay RSS has :not attracted its armature the relay RG4 inthe third group .selector can not attract its armature. The switching operation of the third group .selector willthus be analogous to the switching operation of the second group selector according to the description above, only with the difference that'the selector 'is set by 4the ourth digit in the subscribefs number instead of by the third. Furthermore therelay RG4 receives current over the connection n instead of over the connection m. When the switching operation of the third .group selector begins, the relay RG2 attracts its armature andthe contact 2li is broken. The relayRGll` remains magnetized since the self- 'held contact 43 is closed. The relay RS4 in Fig. 1, however, releases its armature and is disconnected from the b-line since contact 42 opens. The ccntact 4| closes the connection over the b-line.

The communication may now be extended over `the third ygroup selector to a inal selector being set by' means of two further digits in the subscriber-fs number.

The invention may oi course be used in many dierent ways. they third group selector in the. .description above may be.` substituted by a nalselector `for 20.6. lines, and the signal .of the Vceline may attuateVA a relay controlling the final selector to the one or .other hundred, for instance 4by having the nal selector-.in the pause between the two Alast digits iin the subscribers number step lostepsin the line group: oi" 2li-lines deterfinal selector-'corresponding to relay RG4 in Fig. 2.

Fig. 3 shows a nal selector which under influence of a signal from the registering device in Fig. 1 in the pause between the two last digits in the subscribers number is stepping forward steps and which then by the impulse series corresponding to the last digit is set to a line within another group of lines than the one within which the selector would have been set if the above mentioned signal did not exist.

Here is supposed that the final selector according to Fig. 3 is selected by another group selector according to Fig. 2, in which the connection m is laid, but not the connection n. Thus relay RVI attracts its armature and the contacts I i-I4 are actuated. The impulse series corresponding to the last digit but one in the subscribers number vcomes in over the line d, contacts I2@ and 68,

through winding on magnet XMV, to negative. Magnet XMV attracts its armature and moves the final selector one step. Contact I3! is actuated. Parallel with the winding on magnet XMV the relay RVS receives current through its one winding, attracts its armature and becomes, due to contact 84 being closed, slow-releasing and thus the armature of the relay is closed during the whole incoming impulse series. Contacts Ill- 8f3 are actuated. After the end of the impulse series the relay RVB releases its armature and the following circuit is formed: positive, contacts I .'i and 46, winding on relay RVS, contacts 82, I2I, I3I and |23 to negative. Relay RVS attracts its armature. Contacts iii- 59 are actuated. Thus the following circuit is completed: positive, contacts 57, III and IE5, winding on relay RV?, b-line. If no signal exists on the b-line the relay RVZy is not actuated and the next impulse series comes into the following circuit: d-line, contacts 65, 58 and 15, winding on magnet YMV, to negative. The magnet YMV attracts its armature and moves the wiper set of 'the select-or one step in the direction of motion corresponding to the magnet YMV. The contacts I2 i-IZ are actuated. Parallel with the winding on magnet YMV relay RVSI again receives current, attracts its armature and holds it during the whole incoming impulse series. Contacts 8I-8 are actuated. Relay RVG is during the impulse series held through the following circuit: positive, contacts I3 and 64, winding on relay RV, contacts 83, I`24, I3I and I22 to negative.

If, the contrary, there is a signal on the b-line the following circuit is completed when relay RVS attracts its armature: negative, winding on relay RS4 inFig. 1, contacts B2, 34, 4I and 62, the b-wiper of the group selector GVI, contact 22 in Fig. 2, the b-wiper of the group selector GVII, b-line in Fig. 3, Winding on relay RVT, contacts IE5, III and 51, to positive. Relay RV'I attracts its armature and contacts 'iI-l5 are actuated. Relay RVS is self-held through a circuit frorn positive over the contacts 5l and 73, winding on relay RVS, contact 25, to negative. The following circuit is formed simultaneously:

positive, contacts 5l, I I E, I 4I and 74, winding on magnet YMV, to negative. Magnet YMV attracts its armature, moves the wiper set of the iinal selector one step and actuates the self-breaking contact i4 I. The last-mentioned circuit is broken by the contact Uil, magnet YMV releases its armature, contact I4i closes and so on. The magnet YMV moves the wiper set of the iinal selector until the contacts III-I I2 are actuated by a stud accompanying the wiper set. Thus the self-operating current is broken by the contact III. Contacts I2I-I26 were actuated when the self-operating movement began and thus the relay RVI is self-held over contact 12. When contact II opens, the relay RV'I releases its armature, the self-held current of relay RV, however, being still closed over contact II2. When the second impulse series comes in, the relay RVB and its contacts 8I-84 are actuated. Relay RVZ attracts in the following circuit: positive, contacts I3 and S4, winding on relay RVZ, contacts I24, ISI and |22, to negative. Relay RVZ attracts its armature and the contacts 2 I -25 are actuated. The wiper set of the selector is stepped out, the self-held current of the relay RVS is broken in contact 25 but the relay is held by current over the contact 83 until relay RVS releases its armature after the end of the impulse series.

Relay RV is slow-releasing and thus the following test circuit is completed during a short moment of time when relay RVS releases its armature: positive, contact I2, 4winding on relay RV4, resistance rl, contacts 63, 'il and BI, the c-wiper of the final selector, to negative over a. device on the line to which the selector had been set. Ii the line is free, relay RV4 attracts its armature and the contacts 4|-46 are actuated. The ringing current is connected to the line in the following circuit: M+, winding on relay RV3, contacts 36 and 4I, the wipers of the selector and the line, contacts 42, 34 and 23, resistance r6 to the ringing generator RG. On relay RVS releasing its armature the circuit of the relay RVZ, which is slow-releasing is broken, since contact 64 opens. Relay RVZ releases its armature and the ringing signal is switched from a continuous ringing over the contact 23 to the intermittent ringing over the contact 22 and winding on relay RV3 to the impulse device RGZ. Relay RV3 is provided with a cupper casing and thus it is not actuated by the alternating current. Simultaneously with the ringing signals buzzer signals are induced to the speaking lines a and b between windings on relay RVS through the following circuits: positive, primary winding on relay RV5, contacts 62, 54, 44 and 31, to the buzzer generator S153; a-line, secondary winding on relay RVS, a condenser, contact 32, to b-line. 'I'he buzzer signals are heard by the calling subscriber. When the called subscriber answers, the ringing circuit is closed for direct current in the subscribers telephone and relay RV3 attracts its armature due to current from a direct current source connected in a known way between M+ and RGL Contacts Si-Sl' are actuated and the talking connection is closed by the contacts 3| and 33. The ringing current and the buzzer signals are disconnected. Relay RV3 is self-held with current over the resistance 15 andthe contacts iI and 35.

If the called line had been busy, the test relay RV@ would not have attracted its armature during the release time of the relay RVQ. A busy signal would have been connected to the speaking lines through the following circuit: positive, primary winding on relay RVS, contacts 62, 54, 43 and 24, to the buzzer signal generator Sui. The relay RVZ would have been actuated with current over contact 46 and no talking connection set up.

At trunk connections over the final selector according to Fig. 3 also a signal has to be transmitted to the final selector independent of the above-described signals for indicating different line groups, said nal selector indicating that the connection is a trunk one. Here is supposed that negative on the a-line during a moment of the time for the setting of the nal selector is indieating a trunk call. When relay RV'I in Fig. 3 attracts its armature, relay RS4 in Fig. 1 also attracts its armature. Thus the contacts 44 and 45 are actuated and the a-line is connected to a signal line S. If the link circuit according to Fig. l is a trunk link circuit, the line S is connected to a signal device connecting negative to the a-line. Thus a circuit over the a-line is closed through a winding on relay RV5, over contact 6l to positive. Relay RV5 attracts its armature and is self-held in series with the resistance 1'5 with current over the contacts Il and 5|. When relay RVB releases its armature relay RV4 receives current through the following circuit independent of the fact if the called line was free or not: positive, winding on relay RV5, contacts 52 and 53, winding on relay RV4 to negative. Relay RV4 attracts its armature, `if so has not happened before. The c-wiper of the ilnal selector is switched by the contacts 55 or 56 so that a new trunk test circuit, which is not shown in the figures, is formed over the d-line and the contacts 66 and 55. At the same time relay RV3 receives current in series with the resistance 1'5 over the contacts I l and 52 and attracts its armature so that the speaking lines a and b are switched to the trunk link circuit.

The description above relates to an automatic system with step-by-step driven selectors being set directly by the impulses from the dial of the subscriber. The invention may, however, also be applied to automatic systems with machinedriven selectors and to automatic systems with registers controlling all or certain selector steps. The first digit has not to be registered in a registering device belonging to a rst group selector but may as well be registered in a registering device common to a plurality of first group selectors, said registering device being either connected to a number of group selectors in a sti connection or connected to a call by aid of some searching device. Not only the first digit has to be registered but all the digits in the subscribers number may be registered in a register, from which the signals to the selectors for division of the group of lines in dependence of the rst digit may be sent out in correspondence with the description above, whereas the following digits are controlling the setting of the selectors through discriminating devices in the register.

In the description above and on the drawings the lines in those groups of lines which can be reached by the selecting devices, are arranged in a row so that the lines are passed in a certain order by the wipers of the selecting devices. This is of course not necessary for the invention but 10 the selecting devices may as Well be performed with for instance two sets of wipers, which each simultaneously is magnetizing a part of a group of lines whereas the separating signals are indicating which wiper set is to take part in the switching operation.

I claim:

In an automatic telephone system, a calling subscribers telephone set, a connecting link including an impulse relay, means controlled by the initiation of a call from said subscribers telephone set for connecting said telephone set to said impulse relay, a register connected with said link and arranged to be set in one of a number of possible positions in accordance with a rst impulse series from said telephone set transmitted by said impulse relay, a plurality of automatic two-motion switches, means controlled by said switches for establishing a train of selection stages for connecting said telephone set with the telephone set of a called subscriber, means for setting a communication from said link over one of said switches in a rst selection stage in said train in accordance with a second impulse series transmitted by said impulse relay, means controlled by said one switch for selecting a twomotion switch in a succeeding selection stage, means controlled by a third impulse series from said telephone set for setting said last named two-motion switch in its first motion, a set of contacts in the last-named two-motion switch arranged for operation by said switch when the latter has passed a predetermined number of lines in its second motion, a marking relay connected to said last named two-motion switch, means controlled by said register when set by said rst impulse series in a certain one of its positions for closing a circuit to said marking relay, and means controlled jointly by said marking relay and said set of contacts for advancing said last named two-motion switch past said predetermined number of lines in its second motion.

ERIC ARVID ERICSSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

